Some pollsters have warned that Labour’s current ratings may even be too high.

Commenting on the latest poll from ICM, which shows the Tories on 40 per cent and Labour on 35 per cent, ICM director Martin Boon said: “This may be overstating Labour’s strength. 35% is probably too high.

“We can see in the small print of this poll that we’ve still got too many respondents who recall voting Labour.”

ICM has adjusted its methods since the general election in an attempt to better reflect the views of people who decline to reveal their intention.

Labour’s current poll deficit of eight points is not the biggest the party has experienced while in opposition. The Tories enjoyed a 10-point lead just 12 months after winning the 1959 election, for example.